U.S. Pat. No. 4,624,654--Boyd et al, assigned to the assignee of this invention and incorporated by reference, describes a line for manufacturing draw tape bags from a continuous web of thin plastic film. The plastic film web is fed from a supply roll and drawn through an upstream portion of the line, including a first group of work stations, by means of a first pair of input nip rolls which are continuously rotated. The continuous plastic web is intermittently advance away from the nip rolls and through a second group of work stations in a downstream portion of the line by a second pair of intermittently moving nip or draw rolls. The continuous web is accumulated between the input nip rolls and the downstream work stations in a dancer. Several other guide rolls are provided between the dancer and the draw rolls in order to guide the intermittently advanced plastic film web through the downstream portion of the line.
It has been found in operating a bag machine line of the type described in the aforesaid U.S. Pat. No. 4,624,654 at higher cycling speeds, that the inertias associated with the oscillating dancer cause film web bounce and widely varying tension in the film web which affects film tracking, wrinkling and operations such as the tape presealer which is located between the input nips and the draw rolls. These adverse effects resulting from the introduction of varying tension in the film web, limit the maximum speed at which the web can be intermittently advance, and thus the cycling speed of the line.
An object of the present invention is to remove the dancer inertia load from the film web by mechanically coordinating a take up roll position with the bag machine index and hence eliminate the ill affects of web bounce from the operation.